1. Technical Field
The present invention relates to methods and arrangements for indirectly determining the amount of fluid contained in a tank onboard a marine vessel; more particularly, the invention relates to ways of providing level readings of onboard carried fluids such as fuel and potable water to the operator of a marine vessel that are not effected by the operating conditions of the vessel at the time the reading is desired.
2. Background Information
A common malady that operators of marine vessels, and particularly sport craft, have traditionally had to endure is an inability to obtain accurate readings of fill conditions of fluid tanks carried on the vessel. The problem lies not only with fuel tanks, but also with other fluid carrying tanks such as those for potable water.
The inability to obtain sharp readings of carried fluids on a continuous basis depends on several characteristics that are often unique to marine vessels, and particularly to smaller sport-type boats. Among other characteristics, these types of sport boats often travel at high rates of speed, and because of their comparatively small size, are radically affected by the conditions of the water upon which the boat is traveling.
For those persons who have been passengers on such boats in rough water, the fact that fuel in the fuel tank is splashing about is easy to imagine. Similarly, sport boats are often used in activities requiring frequent speed changes and rapid accelerations, as well as decelerations. An exemplary activity that necessitates this type of operation is water skiing.
Still further, for those persons familiar with typical float-based fuel gauges that are traditionally used to measure remaining fuel amounts in a boat's tank, the likely inaccuracy of the readings obtained from the splashing about fuel during rough water travel is also clear.
Another unique characteristic of these types of sport boats is that the attitude; that is, the relative angle with respect to horizontal at which the boat is normally positioned is rarely constant, at least during travel. Moreover, the attitude of the boat is almost never the same under any travel conditions as to when the boat is at rest in the water.
The dynamic nature of fluids held in tanks onboard sport boats, especially when coupled with the fact that the boat is rarely oriented during travel as it is when at rest at best creates consternation for the operator who observes the fluctuations reported by some gauges. Worse, however, are the effects suffered by those operators that may be mislead into believing that supplies of certain fluids, such as fuel, are different, for example, more plentiful than that which actually remains in the observed tank.
Another complication to such fluid gauge readings is also frequently encountered on marine vessels. The complication stems from the character of certain fluid tanks that are employed on marine vessels, and particularly on sport boats. Flexible, bladder-style tanks are often utilized on these types of boats. One reason for their use is that the space within which they are accommodated is often of highly irregular shape, and therefore flexible tanks that can assume the shape of their environment are desirable. Still further, it is common for the accommodation spaces to vary from boat-to-boat, even within same makes and models. At least one reason for these variations is that the way the boat is outfitted with options and accessories often effects the accommodation space for the fluid tank. Therefore, actually flexible tanks may be utilized as described above, but construction techniques that facilitate easy adaptation (flexible) to varying receiving space requirements may also be employed, but that render substantially rigid-walled tanks for installation onto the boat.
Several detrimental effects are suffered because of the utilization of non-uniform tanks when accessorized with traditional float-based level gauges. One negative effect stems from the limitation that the boat manufacturer never knows an exact volume contained by a tank of this type, since by its nature, different carrying capacities are determined by the non-uniform space into which that tank is installed. The limitations of conventional float gauges prevents more utility than producing an indication of fullness based on relative position within the tank. Because of these limitations, the boat manufacturer can be at risk when specifying tank capacity to the consumer. Still further, there is no accommodation for allowing the end user to make such a specification after purchase, for instance, when the capacity is learned upon the first fill-up of the tank if fluid input is otherwise measured; for example, via a dispensing pump.
Another of marine onboard tanks malady is that the contained volume within the tank is rarely uniform with respect to any axis, and especially with respect to a vertical axis along which traditional float-based gauges act. This means that uniform movement of the float gauge can not report uniform changes in fuel level thereby introducing inaccuracies that can prove unacceptable, or at least cause users to seek out better systems. This can be especially important if buyers choose one boat over another because of the type of reporting they can expect with respect to the boat's fluid gauge reporting capabilities.
It should be appreciated that merely smoothing or filtering the fluctuations effecting the float of a conventionally designed gauge is not sufficient. The operational characteristics of marine vessels, and particularly that of sport boats which can cause extreme turbulence and the splashing about of fluids in onboard tanks undermines the benefits that can be expected in other less active environments. Still further, these characteristics prevent the application of most, if not substantially all solutions developed for other vehicular environments. This includes land vehicles and aircraft because these types of transports predominantly travel at reasonably constant rates of speed on relatively smooth courses, at least in comparison to sport water craft.